Expand and combine like terms. $(5-2x^4)(5+2x^4)=$
Solution: We can expand this expression like any product of two binomials. However, this expression has a special form that makes it easier to expand. This is the "difference of squares" form (where $P$ and $Q$ can be any monomial): $(P+Q)(P-Q)=P^2-Q^2$ $\begin{aligned} &\phantom{=}(5-2x^4)(5+2x^4) \\\\ &=(5)^2-\left(2x^4\right)^2 \\\\ &=25-4x^{8} \end{aligned}$